When world leaders gather at the United Nations in New York this September for Ban Ki-moon’s Climate Change Summit, it will be the first time in five years that heads of state and government have stopped to focus collectively on the gathering storm called climate change. For a country like my own – lying at an average of just two meters above sea level and already battling the devastating impacts of a warming world – there is no higher calling.

The world has changed a lot since Copenhagen: the science has become more alarming; the impacts more severe; and the politics more potent. The world’s two biggest polluters – China and the United States – have put energy and climate change at the heart of their bilateral relationship. And for the first time, the world’s businesspeople and bankers are saying that climate inaction is an economic risk we cannot afford to take. As former U.S. Treasury Secretary Henry Paulson said in the New York Times last week, “the costs of the policies necessary to make the transition to an economy powered by clean energy are real, but modest relative to the risks.” Suddenly, a new global deal seems to be within reach.

New consensus needed before Paris 2015

We have learnt the lessons of Copenhagen. Few of the world leaders who attended that conference in December 2009 remain in office, and as political momentum builds for a new global climate agreement in Paris in 2015, it is critical that the ultimate decision-makers are exposed to the issues at the heart of the new deal sooner rather than later. Bringing leaders together at the eleventh hour didn’t work last time, but this time we have an opportunity to get on the same page a year in advance. With a clear mandate for an ambitious new deal, our ministers and negotiators will work harder and faster over the coming year to seize this once-in-a-generation opportunity to set global emissions back onto a saner, safer path.

As all of us know, diplomacy at the highest levels is most of all about being in the room with your counterparts to debate the issues and find common ground. If President Obama wants his Climate Action Plan to be about action at home and abroad, he will join me in New York. If President Xi wants clean air for the more than 1.3 billion people in his country, he will be there too. If Prime Minister Cameron understands that the UK’s devastating floods earlier this year were a sign of things to come, then he will be there. And if Prime Minister Tony Abbott truly believes that his Direct Action Plan and carbon price reversal stand up to global scrutiny, then he will be there as well.

The reality is that every world leader and every country in the world would benefit from ramping up action to tackle climate change. We are currently on the way to four degrees of warming, which would wreak havoc in every corner of the globe. We can and we must do better. All of us need to heed the Secretary-General’s call, and come to New York armed with “bold new actions and partnerships” to accelerate climate action. By September, we must be ready to embrace the economic transformation to achieve carbon neutrality by the middle of the century.

Island nations committed to climate leadership

This is exactly what our Majuro Declaration for Climate Leadership – the big outcome of last year’s Pacific Islands Forum Leaders’ meeting, held here in the Marshall Islands – sought to do. As a group of political leaders determined to stave off the dangers of the ever-rising seas, we committed ourselves to climate leadership through bold emissions reductions and renewable and energy efficiency targets, and called on others to do the same.

Looking forward, we hope to deepen these targets, recognizing that there is no group of countries in the world where the win-win for the economy and the environment that comes with the shift to clean energy is more profound than in Small Island Developing States (SIDS), particularly in the Pacific. With this in mind, we are working with the International Renewable Energy Agency and our development partners to launch a SIDS Lighthouses Initiative at the Summit in September, putting SIDS at the cutting edge for the demonstration and uptake of renewable energy technologies, both tested and new.

World leaders must seize opportunities

Thankfully, the rest of the world is beginning to follow our lead. This year, President Obama announced new regulations to phase out dirty coal, China said it wants to triple solar power by 2017, and Germany continues to set world records for the production of renewable energy. The story of climate change is quickly becoming one of economic opportunity, and no country should risk being left behind.

As world leaders, we expect to be judged by history, and by the decisions we take at pivotal moments. This September will be a test for us all. Are we willing to let another decade slip away, standing idly by as the world’s most vulnerable countries and people, including my own, fight a losing battle against the king tides and typhoons of a warmer world? Or will we instead stand together and say we are ready to embrace a carbon-free future, and to do it today? With just 18 months to go before our deadline in Paris, Ban Ki-moon’s Summit is our chance to be the leaders we were elected to be. We must all be there.